Centrifugal diffuser type vapor separating pump



Jan. 26, 1960 M. L. EDWARDS 2,922,375

CENTRIFUGAL DIFFUSER TYPE VAPOR SEPARATING PUMP Filed Sept. 11, 1953 3 Sheets-Sheet 1 ETFEEZET M/ea Lowe/Z Edwards b /H J Jan. 26, 1960 M. L. EDWARDS 2,922,375

CENTRIFUGAL DIFFUSER TYPE VAPOR SEPARATING PUMP Filed Sept. 11, 1953 3 Sheets-Sheet 2 272's his? M765 Lowell Edwards Z Z E Jan. 26, 1960 M. EDWARDS 2,922,375

CENTRIFUGAL DIFFUSER TYPE VAPOR SEPARATING PUMP Filed Sept. 11, 1953 3 Sheets-Sheet 3 W F? 6 7a 1 m 751 11 725 iii ET Miles Laws/l Edwards United States Patent CENTRIFUGAL DIFFUSER TYPE VAPOR SEPARATING PUMP Miles Lowell Edwards, Portland, Oreg.

Application September 11, 1953, Serial No. 379,642

12 Claims. (Cl. 103-113) This invention relates to vapor separating pumps with large end-to-end vapor separating chambers in the impeller thereof which discharge the separated vapors laterally out of the pumps. Specifically, this invention relates to vapor separating pumps having centrifugal diffusers which discharge the separated vapors laterally from the separating chambers of the pump impellers around the periphery of the pump under positive centrifugal force.

The present invention now provides vapor separating pumps with impellers having large vapor separating chambers throughout their entire axial length. These chambers are unimpeded and open from end-to-end to permit free passage of vapor. Vapors from these chambers are diffused out of the pumps in a lateral direction around the periphery of the pumps thereby minimizing head room requirements. The discharge of the vapors under the influence of centrifugal force maintains a more sustaining effect on the flow of fluid through the diffuser. Since the diffusers discharge laterally, the pumps of this invention can have inlets in the top and bottom thereof. In such double entry pumps of this invention, a separating wall is provided on the impeller to divide the impeller chamber into'upper and lower compartments but the end-to-end vapor separating chambers are not blocked by this wall. In this manner, the exposure of the upper compartment above liquid level will not break the primein the lower compartment and the pump will continue to operate until the lower compartment is also above liquid level.

Pumps of this invention also include single entry pumps and double entry pumps equipped with a separate diffuser chamber for each entrance.

It is then an object of this invention to provide a vapor separating pump with a laterally extending annular vapor passage having diffuser vanes shaped for centrifugally discharging vapors after they are separated from the liquid being pumped.

Another object of this invention is to provide a vapor separating pump which difiuses vapors laterally out of the pump around the periphery of the pump.

A further object of this invention is to provide a vapor separating pump having an impeller with large end-to-end vapor separating chambers discharging into a peripheral diffuser under centrifugal force induced by the impeller.

Another object of this invention is to provide a vapor separating pump which diffuses vapors with a centrifugal propelling force.

A still further object of this invention is to provide a double entry vapor separating pump having a peripheral vapor outlet.

A specific object of the invention is to provide a double entry vapor separating pump with a barrier wall dividing the inlets of the pump into upper and lower compartments whereby the pump will continue to function even though the upper compartment is exposed to air.

A still further specific object of this invention is to provide a double entry diffuser type pump which discharges under centrifugal force to the side of the pump.

' ice Other and further objects of this invention will be apparent to those skilled in the art from the following detailed description of the annexed sheets of drawings which, by way of preferred examples, illustrate three embodiments of the invention.

0n the drawings:

Figure 1 is an elevational view, with parts in vertical cross section, of a pump and motor unit according to this invention mounted on the bottom wall of a fuel cell.

Figure 2 is an enlarged transverse cross-sectional view taken along the line II-II of Figure 1.

Figure 3 is a bottom plan view of the impeller in the pump of Figure 1.

Figure 4 is a side elevational View of the impeller of Figures 1 and 3.

Figure 5 is a fragmentary enlarged vertical cross-sectional view of a portion of the pump of Figure 1.

Figure 6 is a fragmentary vertical cross-sectional view similar to Figure 5 but illustrating a modified embodiment of the pump including two diffuser chambers for the pump.

Figure 7 is a fragmentary vertical cross-sectional view of a single entry pump and motor unit according to this invention.

Figure 8 is a bottom plan view, with parts in horizontal section, of the impeller in the pump of Figure 7.

Figure 9 is a transverse vertical cross-sectional view taken along the line IX-IX of Figure 7.

Figure 10 is a fragmentary vertical cross-sectional view of a single top entry pump.

Figure 11 is a top plan view of the impeller in the pump of Figure 10.

As shown on the drawings:

The pump and motor unit 10 of Figure 1 is illustrated as mounted on the bottom Wall 11 of a fuel cell to communicate freely with liquid in the cell for pumping vaporfreed liquid out of the cell while returning the vapors to the cell. The unit 10 includes a base 12 spanning an opening 11a in the bottom wall 11 and anchored to this bottom wall for carrying the unit inside of the tank. The base 12 has a gasket 13 around the top marginal periphery thereof. This gasket sealingly engages the bottom 11 of the cell around the opening 11a. A mounting ring 14 is mounted on the bottom 11 and receives cap screws 15 extending from the base. In this manner, the base is rigidly affixed to the bottom of the tank.

The base 12 has a central sump portion 16 in full communication with the bottom of the cell. A drain outlet 17 closed by a plug 18 is provided on the bottom of the sump 16.

A discharge nipple 19 is integrally formed'on the base alongside of the sump 16 and one or more legs 20 project upwardly from the base to cooperate with the nipple 19 for supporting a pump casing 21 in spaced relation above the sump. The leg or legs 20 also support a motor casing head 22 receiving a motor 23 in bolted relation thereon.

The pump casing 21 is a cylindrical housing with a central bore 24 therethrough and having an annular volute chamber 25 therein around the bore 24 near the upper edge thereof. A neck portion 26 provides a passageway 27 joining the volute chamber '25 with the interior of the nipple 19. This nipple can have either end thereof receive a discharge fitting. As illustrated, a closure plug 28 closes the bottom end of the nipple and the top end of the nipple receives a discharge fitting 29 connected with a discharge fuel conduit (not shown).

The bore 24 of the housing 21 receives athroat ring 30 in the lower portion thereof. The throat ring 30 has an outturned flange 30a anchored to the bottom face' of the casing 21 by screws 31. The throat ring 30 has a bell-shaped inlet mouth 32 converging to a flat'shoul- 3 der 33. The shoulder 33 extends to a diverging side wall 34 which terminates at a flat top 35. This flat top 35 is at a level intermediate the top and bottom of the volute chamber 25.

The top of the pumpcasing 21 receives thereover and-therein a diffuser disk 36 having apilot portion 37 fitting snugly in the top endof the bore 24 and-having a shoulder 38 fitting over the top of thecasing 2'1. This diffuser disk 36 has a bell-shaped central mouth-39- converging to a flatv outturned' shoulder 40 which extendsto a diverging wall '41 that terminates in a flat bottom 42 in spaced parallel relation above-the top 35 of the throat ring; The dilfuser disk 36'is securedto thezcasiug 21 in any suitable way such asby meansof screws 43 or the like A plurality of lateral diffusion passages 44 are provided in the disk 36. As shown in Figure 2, these passages 44 are separated by ribs or diffuser vanes 45 and have side walls of sweeping arcuate shape to produce tangential gaps or passages design for centrifugal discharge. The passageshaveinner ends in advance of the outer ends to diffuse the centrifugally whirling flow from the vanes into a laterally outward flow at high velocity. As shown in Figure 1, these passages 44 have upwardly sloping top walls and are deeper at their outer ends to enhance the lateral flow.

An impeller unit 46 is mounted within the pump casing 21 in relatively close running clearance relationship with the shoulders 33 and 40, the sidewalls 34 and 41, and the fiat walls 35 and 42. This impeller has a central flat dividing wall 47 (Figures 2 and 3) level with'the center of the gap between the walls 35 and 42. A hub 48 is provided on the center of this wall and extends upwardly through the center of the mouth 39. The hub 48 is attached to a drive shaft 49 for co rotation. As shown in Figure 3, a key slot 50 is provided in the wall 47 to key the hub to the shaft. The driveshaft 49 depends from the head 22 of the motor casing and a seal assembly 51 is provided in the bottom: of 'the head 22 to receive the shaft therethrough and prevent leakage of fluid into the interior of the motor compartment. A bearing 52 is also carriedby the head 22 for the shaft. Theshaft is driven by the armature of the electric motor 23.

As best shown in Figure 3, sprockets 53 project from the periphery of the wall 47 and carry at their outer ends thetrailing ends of upstanding-vanes 54. As shown in Figure 4, these upstanding vanes have narrow upright outer trailing ends 54a extending on both sides of the sprockets 53. These outer ends 54a have flat parallel top and bottom edges 54b for close running clearance relationship with the wall portions 35 and 42 as shown in Figures 1 and 5. The ends 54a terminate adjacent the inner periphery of the volute chamber 25 and the narrow portions of these trailing ends ride in the 7 gap provided between the diffuser disk and the throat ring. The parallel top and bottom edges 54b merge into diverging edges 540 which. have close running-clearance relation with the wall portions 34 and 41 as shown in Figures 1 and 5. Relatively Wide vane faces-54d are provided betweenthese diverging edges 54c and-these wide portions 54d have curved front faces desi-gned for centrifugal discharge as they are rotated in aclockwise direction as viewed in Figures 1 and S or in a counterclockwise direction as viewed in Figure 3. The contour of the wide faces 54d is continued in the narrow trailing portions 54a between the edges 5412.

- The edges 54c diverge to inwardly offset ribs 54c of upstanding flat faced vane. portions 54f which are anchored at their midpointsto the wall 47. These portions 54 have sharp vertical leading edges disposed-just inwardly from the periphery of the dividing wall 47 as best shown in'Figures 2 and 3. The-offsets 542 are in tegra-I with the sprockets- 53 while the portions-54f are integral with the separating wall 47 just inside of the periphery of this wall. Thus, each blade 54 has an ofifset leading edge anchored to a sprocket and a narrow trailing edge anchored to the next adjacent sprocket. The distance between the top and bottom edges of the vane portions 541 extends the full height of the space between the shoulders 33 and 40 and has close running clearance relation therewith. The trailing edge, on the other hand, extends into the gap between the walls 35 and 42.

The vanes 54 are thus arranged in a ring around the dividing wall 47 and extend equidistant on opposite sides of this wall to provide vertical sharp leading edges just inwardly from the periphery of the. dividing wall and merged through substantially radially extending olfset portions 54:: to pumping faces 54d which converge to narrow trailing edges for discharging into the volute chamber. The leading edges are radially inward from the trailing edges and the vane shape is such as to slice oif liquid entering the pump through the bottom mouth 32 and the top mouth 39 and discharge the liquid into the volute chamber while separating bubbles of vapor from the liquid under the influence of centrifugal force.

As shown in Figure 3 open vertical channels 55 are provided'bet'ween the wall 47 and the inner faces of the ends and at their tops communicate with the diffuser passages 44. The large channels extend from one end to the other endof the impeller and permit free passage of vapor so that-only one diffuser outlet is necessary to remove vapors generated at both ends of the impeller.

The large channels are provided by the spoke-like projections from the hub which have inner portions anchoring and supporting the leading part of one vane and then extend outwardly to support the trailing end of the preceding vane.

In operation the pump is submerged in liquid such as gasoline, in the fuel cell and this liquid freely enters both the top and bottom inlets of the pump to fill the chambers above and below the wall 47. These chambers are surrounded by the ring of pumping vanes and when the impeller is rotated, this liquid is sliced off by the leading vane edges 54; and the outer periphery of the column of liquid is caused to rotate by the offset portions 54e of the leading edges 54 The rotating annulus of liquid is flung outwardly by centrifugal force and is propelled by the blade faces 54d and 54a into the volute chamber. However, the lighter gases entrapped in the liquid lag behind the heavier liquid material and rise in the channels or passages 55-to be centrifugally discharged through the diffuser passages 44 to the outside of the pump.' The diffuser passages are shaped to expedite centrifugal discharge of the gases. Therefore, the separated vapors and gases are positively ejected under the influence of centrifugal force and are discharged laterally of the pump while the top and bottom of the pump is free to receive liquid. The fully liquid material pumped into the volute 25 is discharged through the passage 27 and into the nipple 19.

In the event the top mouth 39 of the pump is exposed to air as when the liquid level in the fuel cell falls below this top mouth, the dividing wall 47 will prevent the pump from losing its prime and it will continue to operate as long as it receives liquid from the sump 16. Since this sump 16 is actually below the bottom level'of the fuel cell, the pump is effective to completely empty the fuel cell.

In the modification shown in Figure 6, the unit 10a has elements thereof identical with those illustrated in Figures 1 to 5 marked with the same reference numerals. In the modification 10a, however, the throat ring30' has diffuser discharge passages 56 provided therein to re ceive the vapors from the channels 55 adjacent the lower ampere ends of the channels. These passages 56 are arranged in the same manner as the passages 44 shown in Figure 2 and function in the same manner. The channels 55 of the impeller, therefore, have top and bottom diffuser discharge passages. Therefore, the vapors in the channels 55 can discharge out of both ends of the channels. Otherwise, the pump operates in the same manner described above in connection with Figures 1 to 5.

In the modification c shown in Figures 7 to 9, a single entry pump is provided. As illustrated in Figure 7, a casing 57 has a volute chamber 58 around the inner periphery thereof and receives a bottom throat ring 59 having a bell-shaped mouth 60 converging to a flat shoulder 61 which shoulder in turn, extends to an outwardly sloping side wall 62 terminating in a curved top 63 above the bottom of the volute chamber 58. A diffuser passage-containing wall 64 is provided on the casing 57 and has passages 65 therethrough similar to the passages 44 shown in Figure 2 but having an upward slope. Slopes of from to 28 degrees from the horizontal have been found to be satisfactory.

The center of the wall 64 has a counter-bore 66 merging with a bore 67 of the casing. The counterbore 66 receives the hub 68 of an impeller 69 mounted on a drive shaft 70 of a motor 71 in the casing. As illustrated, the motor field can extend down to the wall 64 and the motor bearing 72 can be closely adjacent the hub 68. In this arrangement, head room requirements are minimized and the entire pump and motor unit can be made very short to fit in low tanks.

The impeller 69 has a radial hub flange 68a in the counterbore 66 surrounded by a ring of spokes 73at a level beneath the flange. These spokes have pumping vanes 74 depending therefrom. These vanes 74 have narrow vertical trailing edges 74a fitting in the gap between the walls 63 and 64 to discharge into the volute chamber 58. The vanes increase in height to follow the contour of the wall 62 of the throat ring 59 and provide wide pumping faces 7411. These pumping faces extend between the spokes 73 and the shoulder 61 of the throat ring. The forward ends of these vanes are inwardly offset as at 74c and the inner offset ends have pointed forwardly extending leading ends 74d. The portions 74c and 74d extend above the spokes 73 into the counterbore 66 and are secured to the hub flange 68a. This provides an angle section correction between the hub flange and the main part of the blade system which gives a desired structural strength for withstanding operating stresses. The leading ends of the vanes 74 are thereby rigidly secured to the hub inwardly and above the spokes while the trailing ends of the blades are secured to the spokes 73 outwardly from the hub. The inner ends of the vanes are relatively deep while the outer ends are relatively shallow.

Vertical channels 75 are provided between the inner ends of the vanes bounded by the inwardly offset vane portions 74c. These channels 75 have full open communication at their top ends with the diffuser passages 65 because the hub flange 68a is above the entrance mouths 76 to these passages and the spokes are below and radially outward from these entrance mouths. Thus, the upwardly rising and rotating vapor-rich columns of fluid in the channels 75 will be flung into the entrance mouths 76 of the passages at the tops of the channels.

In operation, fluid entering the volute mouth 60 fills the space inside of the ring of vanes to form a column of liquid. The leading ends 74d of these blades then slice off liquid from this column inside the pump and the offset portions 740 rotate this liquid. As the liquid is rotated it is centrifugally thrown outwardly and follows the outer faces 74b of the pumping vanes to the trailing edges 74a where it is discharged into the volute 58. The centrifugal action, however, separates the heavier liquid from the lighter gases and vapors entrained in the liquid and thesases and vapors rise through the channels 75 as a rotating lighter mass. As soon as the rotating lighter mass in the channels reaches the 'level of the entrance mouths 76 to the passages it is discharged under the influence of centrifugal force through the passages to the side of the pump. Therefore, the pump separates gases under the positive force of centrifugal action and then also discharges the gases under this positive force.

In the modification 10d of Figures 10 and 11, a top inlet pump is provided with a centrifugal vapor diffuser in the top end thereof. As shown in Figure 10, a pump casing 81) has a volute 81 surrounding an open topped central pumping chamber 82 and in communication therewith around the bottom thereof through a narrow gap 83. Laterally extending centrifugal diffuser passages 84 radiate from the upper portion of chamber 82. These passages are similar to the passages 44 or 65 of the pumps described hereinabove. An inlet throat 85 is provided at the top of the casing to be submerged in liquid to be pumped.

The impeller 86 for the pump 10d has a central hollow hub 87 extending through the central portion of the pumping chamber and carrying a radially extending flange 88 on the bottomend thereof. This hub 87 is adapted to be attached to the drive shaft of a motor or the like.

'The bottom flange 88 has spokes 89 radiating therefrom carrying an upstanding ring of pumping vanes or blades 90 in spaced relation around the hub 87 and closely fitting the wall of the pumping chamber 82. Each blade 90 has an inwardly offset portion 90a with a forwardlyprojecting end 90b. The bottom of the portions 90a and 90b are anchored to the inner ends of the-spokes 89. The spokes then project outwardly from these portions of the blade to the trailing end portion 90c of a preceding blade in the ring. This trailing end portion 900 is relatively narrow and fits in the gap 83 as shown in Figure 10.

The blades have relatively wide faces 90d between the offset portions 90a and the trailing portions 90c. Vertical channels are thus provided between the offset portions 90a. These channels communicate at their outer ends with pumping channels between the broader faces and narrow trailing ends of the blades. The inner vertical channels, however, have full open communication at their top ends with the diffuser passages 84.

Fluid entering the inlet throat of the pump 10d will fill the pumping chamber to form a central column or" liquid. The inwardly offset portions of the blades v will slice off liquid'from the periphery of this central column in the pumping chamber. The sliced off liquid will be caused to rotate by the offset portions 90b and as it rotates, it will be flung outwardly through the pumping channels between the blades into the gap 83 and thence through the volute chamber 81 to the discharge outlet of the pump. Moreover, the rotating fluid will also have its lighter constituents separated from its heavier constituents by the action of centrifugal force in the channels between the offset portions. This lighter fluid will rise in the channels until it reaches the diffuser passages 84 whereupon it will be flung outwardly through the passages to be discharged around the periphery of the pump casing 80.

The pump 10d requires a minimum of head room since the centrifugal diffuser passages extend laterally and surround the pumping vanes.

From the above descriptions it will be understood that this invention now provides an eflicient vapor-separating pump which discharges vapors under positive centrifugal action in a lateral direction around the periphery of the pump casing from large vapor-separating channels which are unimpeded along their length and which have free, unobstructed communication with the radiating diffuser passages.

The impellers for the pumps of this invention are light in weight because they are constructed from a amount of metal and yet have enhancedmechanicai Strength due to the manner in which the ring of bladesis carried from radiating spokes on a-hub. Each spoke anchors the inner leading end portion of one blade and the outer trailing end portion of a preceding blade. The blades have inwardly offset portions which extend substanti'ally radially to forwardly extending knife-like ends effective to slice off liquid around the periphery of a column of liquid in the pumping chamber. These offset portions have large vapor-separating channels therebetween and extend beyond the liquid pumping portions of the vanes so that the channels will have free, unimpeded open communication with the centrifugal diffuser passages surrounding the inner ends of the vanes.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

I claim as my invention: A

l. A vapor separating pump which comprises a pump casing having a central inlet, a pumping chamber surrounding said inlet in communication therewith around the periphery thereof, laterally extending diffuser passages having inner ends communicating with the inlet chamber and outer ends discharging around the side of the pump, a vapor separating impeller rotatably mounted in the pump, said impeller having a ring of pumping vanes with shallow trailing ends extending intothe inlet of the volute chamber and deep forward ends extend ing vertically throughout the entire height of the inlet chamber to slice off liquid from the column therein, vertical channels behind-said vanes communicating with the diffuser passages, and the deep forward ends of said vanes having inwardly offsetportions to create a ring of rotating fluid in the-channels while discharging the liquid centrifugally into the-volute chamber and the gas rich lighter portion of the liquid into the diffuser passages.

2. A double entry vapor separating pump which comprises a housing having a central passage therethrough with top and bottom inlets, a diffuser passage surrounding said central passage and discharging laterally of the central passage, a pumping chamber surrounding said central passage in spaced separated relation from the diffuser passage and having a peripheral outlet, a vapor separating pump impeller rotatably mounted in said central passage and having a flat barrier Wall dividing the passage midway of its axial length into upper andlower compartments, and a ring of vapor separating vanes on said impeller outwardly from said barrier wall arranged to centrifugally discharge liquid into the pumping chamber and defining axially extending channels communicating with said diffuser passage for discharging gasrich material into' the diffuser passages, said barrier wall being effective to maintain operation of thepumpeven after the top inlet is uncovered, the vanes extending equidistantly on opposite sides of the barrier wall to provide vertical sharp leading edges inwardly from the pe riphery of said wall, said vanes being further-provided with trailing edges radially outwardly of the leadingedges and radially extending offset portions between said trailing and leading edges, said leading edges slicing-oft liquid from the column in the central passage and the outer periphery of said column being rotated by the offset portions and flung outwardly into the pumping chamber.

. 3; A vapor separating pump impeller which comprises a central hub having a flat radialflange, sprockets extending from'the periphery of said flange, and a ring of upstanding pumping vanes having leading end portions attached to the flange and trailing end portions attached to the sprockets, each vane having a leading end'portion securedto one, sprocket and a trailing endportion attached to anadjacentsprocket, said .vanes extending equidistantly on opposite sides of the flange and being arranged spirally around-the. flange to effect centrifugal pumping. and centrifugal vapor separation.

4. A pump impeller for a double-entry. vapor separating pump which comprises a hub having a flat radial flangeQsprockets in spaced relationextending from the periphery of the flange, upstanding: pumping vanes mounted on the sprockets and having deep vertical inner ends on-hoth sides of the flange and shallow trailing ends intermediate the deep inner ends and secured to the flange, said inner ends having radially inwardly offset portions'attached to the sprockets with flat faces adapted for slicing off liquid from acolumn inside of the chambers on opposite sides of the hub flange, and said vanes being spaced outwardly from the periphery of the hub flange to provide open ended vertical vapor separating chambers between said vanes and said flange.

. 5. A diffusion type vapor separating pump impeller which comprises a hub having sprockets radiating therefrom, relatively narrow blades mounted on said sprockets and havingdeep inner ends and shallow outer ends, said blades having radially inwardly offset portions and flat faces on the inner ends-of the offset portions, thesprockets having inner portions supporting the offset portion of one vane and said sprockets extending outwardly to support the outer end of the preceding .vane, .said inwardly offset portions and flat faces coasting with the back faces of adjacent blades-and with the sprockets to define axially extended open channels extending axially through the spaces between the blades.

6. A pump impeller which comprises a hub, a. flat fiange'radiatin-g therefrom, spokes radiating frornsaid flange at spaced intervals around the periphery thereof,

a ring of pumping vanes surrounding thehub. and .ex

tending equidistantly on opposite sides of the flange and mountedon said spokes, each vane having aninwardly offset leading end portion adjacent the periphery/of the flange and anchored to an inner end portion of a spoke, each vane having an outer end portion trailingtheinner end'portion and anchored to theouter end portionof an adjacent spoke, and said vanes having the inner end portions thereof projecting above the trailingend portions toprovide therebetween axially elongated vaporseparating channels.

'7. A vapor separating pump comprising a housing having a central passage thcrethrough and a peripheral volute chamber communicating with said .centralpassage, a diffuser coaxial with said centralpassage and having passages therein arranged to discharge .vapors radially from the pump housing, an-imp'eller rotatablymounted in said central passage and havinga flat central wall dividing said central passage intoiupper. and lower compartments, upright vanes on said impellerarranged in a ring on the wall and extending equidistantly on opposite sides thereof to deliver liquid into.. said volute chamber, said impeller having means definingaxially extending channels radially inwardly of said vanes to.per-. mit passage of gases into said passages in said diffuser.

8;. A 'vapor separating. pump comprising a.housing having a central passage therethrough withtop .and bottom inlets and a peripheral volute chamber communicating with said central passage, a-difiuser coaxial with saidcentral passage and having. passages. therein arranged to discharge vapors radially out of the. pumps, an impeller rotatably mounted in said central passagev and having a. flat central wall dividing said central. passage into-upper and lower compartments, aud -upright vanes on said impeller arranged in a ring onxthe wall and ex tending equidistantly on opposite sides thereof to deliver liquid intosaid volute chamber, saidimpellerihaving means. definingaxially extending channels radially inwardly. of said vanesto permit passage of .gases into said passages in. said diffuser.

9; Avapor separating pump comprising a housinghaving a central passage therethrough ;with top and bottom inlets and a peripheral volute chamber communicating with. said central. passage, a diffuser. coaxial with said central 5 passage andhaving passages therein arranged. to. discharge .vapors radially out of the pump, an impeller rotatably mounted in said central passage and having a central wall dividing said central passage into upper and lower compartments, and upright vanes on said impeller arranged in a ring on the wall and extending equidistantly on opposite sides thereof to deliver liquid into said volute chamber, said impeller having means including the upstanding walls of said vanes defining axially extending channels radially inwardly of said vanes to permit passage of gases into said passages in said diffuser.

10. In a vapor separating pump, a housing having an end inlet opening, a tapered pumping chamber with a gradually increasing diameter inwardly from said inlet opening, and an exterior lateral surface surrounding said pumping chamber; a tapered impeller of gradually increasing diameter rotatable in one direction with close running clearance in said pumping chamber; and a plurality of lateral diffuser passages opening at their outer ends through said exterior lateral surface of said housing at points spaced from said inlet end and opening at their inner ends in portions of said pumping chamber which are swept by peripheral portions of said impeller, said diffuser passages having tangential walls extending forwardly from their inner to their outer ends with respect to the direction of rotation of the impeller.

11. A vapor separating liquid pump comprising a housing and an impeller, said housing having a wall portion surrounding and defining a pumping chamber for said impeller, means for mounting said pump so that the outer surface of said wall portion is submerged in a body of liquid to be pumped, said wall portion having a generally conical inner surface with a gradually increasing diameter in said pumping chamber, said housing having an inlet opening at the small diameter end of said inner wall surface and a volute chamber communicating with said pumping chamber at the maximum diameter of said inner wall surface, said impeller having peripheral portions of gradually increasing diameter rotatable in one direction with close running clearance within said inner wall surface to move said liquid through said pumping chamber from said inlet opening to said volute chamber, and a plurality of generally tangential diffuser passages extending throughout their length in a common plane perpendicular to the axis of the impeller, the outer ends of said passages opening through said outer surface of said wall portion at a distance from its inlet end in unrestricted communication with said body of liquid and the inner ends of said passages opening through the inner surface of said wall portion within the area thereof which is swept by said peripheral portions of said impeller, said tangential diffuser passages having their inner ends beginning in advance of their corresponding outer ends.

12. A vapor separating liquid pump comprising a housing having an end inlet opening, said housing defining a tapered pumping chamber with a gradually increasing diameter inwardly from said inlet opening, said housing having an exterior lateral surface adapted to be submerged in a body of liquid to be'pumped, and a tapered impeller of gradually increasing diameter rotatable in one direction with close running clearance in said pumping chamber, said housing having a plurality of lateral diffuser passages extending therethrough in a forward tangential direction with respect to the direction of rotation of the impeller, said passages having leading inner ends in said housing at said pumping chamber which are. swept by peripheral portions of said impeller and said passages having trailing outer ends opening through an outermost lateral wall surface of the housing in unrestricted communication with said body of liquid.

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